Is the thin wall test manual or automatic?

I make model trains and had one of my models rejected due to thin walls at the end of a blunt point.

Thing is, with my trains certain parts are common to an number of models and I've had several models containing exactly the same part print off successfully only a few days ago.

So is this check something manually done, so the results may depend on the whim of the operator, I'd always assumed it was an automated test.

Which makes me ask the question, once a models been successfully printed is it tested each time or is it flagged that this has been done already? IE. could I get models being rejected that have already been printed?